Windows (Vista and above) and Max OS X allows the user to set a preferred sample rate as "native" rate. Are you saying that we should simply ignore this setting and assume that the user did not know what he was doing when he/she selected a certain rate? If so, what other types of user settings should be ignored; mute, volume levels etc.? If a user has asked for 8kHz as input rate, then the best rate to work with is 8kHz. There is not much we can do about that and the user will have to live with the consequences. On some platforms, it is possible to use an alternative sample rate than the native rate but that has other negative effects.

Again, WebRTC shall work for 8kHz on all platforms but it will not function at its full capacity.

On reading your comments again it seems you are saying it is in the
interest of the user to set a higher sampling rate to enjoy webRTC in
its broader context.

My experience is getting users to understand let alone modify such
technicalities is a non starter.

Surely WebRTC can attempt to address Audio at an acceptable rate
(44.1Khz) rather than simply accept the current rate set and take
remedial action (step down the list) if that fails which is highly
unlikely.